Recent experiments to test the effects of visual deprivation on the development of central visual pathways have unexpectedly demonstrated that infant lid suturing results in the development of severe myopia (-20D average) in the tree shrew, Tupia glis. The effect occurs monocularly, producing adults with one normal and one myopic eye; and since the tree shrew is a prototypic primate with excellent binocular acuity and diurnal habits, we propose to study the inducement of myopia in the sutured eye as model system to advance understanding of the development of myopia in humans. Myopic eyes are currently available to us from animals used in the deprivation studies of Dr. V. A. Casagrande at Vanderbilt, and preliminary experiments are underway. Caliper measurement of the myopic globes indicates that the myopic eyes are axially elongated (mean values of 8.13 mm vs. 7.76 mm for control eyes); but the elongation is insufficient to account fully for the ammetropia, thus indicating a refractive contribution. We intend to determine the sequence of ophthalmic changes which lead to development of myopia by examining tree shrews at various times after lid suturing using modern techniques including retinoscopy, keratoscopy, and ultrasonography. Light and electron microscopy have revealed changes in the connective tissue and vessels of the myopic eyes when compared with controls; and we propose to use morphometric techniques to quantitate the development and extent of these differences. Our current data support the hypothesis that microscopic examination of the lid-sutured eyes will provide anatomic clues to the aetiology of myopia.